Deterministic and Monte Carlo modeling and analyses of YALINA-THERMAL subcritical assembly.

Abstract

The YALINA thermal facility of the Joint Institute for Power & Nuclear Research – SOSNY, Belarus consists of a subcritical assembly driven by a californium, deuteriumdeuterium, or deuterium-tritium neutron source. This study analyzes the YALINA thermal assembly using deterministic and Monte Carlo calculation methodologies. In the deterministic analyses, the DRAGON computer program has been used to generate the macroscopic cross sections starting from the WIMSD nuclear data library with 69 energy groups. The WIMSD nuclear data library has been modified by adding few isotopes describing the polyethylene material, some impurity nuclides, and the uranium nuclides without delayed neutrons for calculating the effective delayed neutron fraction by the k-ratio method and the Bell and Glasstone spatial correction factor. The data added to the WIMSD library have been generated by the NJOY computer program using the ENDF/B nuclear data files. The macroscopic cross sections generated by DRAGON computer program describe more than sixty different zones of the subcritical assembly; in these zones, whenever necessary, the materials have been homogenized. The macroscopic cross sections generated by the DRAGON computer program have been then used in the PARTISN computer program, which modeled the YALINA thermal facility in details. In order to facilitate the coupling between the DRAGON and PARTISN computer programs, a new interface computer program (DRAGON2PARTISN) has been developed. For the time-dependent calculations, the PARTISN computer program has been modified to speed up the computing time. Some of the deterministic results have also been confirmed by the TORT computer program. In addition, the YALINA thermal facility was modeled without any geometrical homogenization by two independent Monte Carlo computer programs, MONK and MCNP/MCNPX. The MONK computer program has nuclear data libraries, which are different from the libraries of MCNP/MCNPX computer programs. The Deterministic and Monte Carlo analyses of the YALINA thermal assembly investigated: the neutron multiplication factor (keff), the neutron source multiplication factor, the effective delayed neutron fraction, the prompt neutron lifetime and generation time, the spatial neutron flux profile, the neutron spectrum, and the He(n,p), U(n,f), Au(n,γ), In(n,γ), and Mn(n,γ) reaction rates profiles, the time dependent He reaction rate from the pulsed deuterium-deuterium or the deuterium-tritium neutron source, and the Bell and Glasstone correction factors for the measured reactivity values. The analytical results have been compared with experimental measurements. This report presents the computational models and the obtained results. The comparison of the deterministic and Monte Carlo results shows an excellent agreement with the experimental measurements.